board: beacon: imx8mm: Let clock system enable UART clock

Now that the UART driver can enable the required clocks, remove
the hard-coded clock enable.  This requires a small re-order
of a couple functions.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
1 file changed